With advances in gene therapy and recombinant DNA technology, protein pharmaceuticals are an important class of therapeutic drugs. For example, pulmonary delivery of therapeutic peptides and proteins has received significant attention in recent years, for the treatment of respiratory illness and as an attractive alternative to injection for the systemic delivery of macromolecules. However, the commercial production of protein pharmaceuticals is severely limited by chemical and physical degradation of the proteins which can lead to biological inactivation (Manning, M. C. et al. (1989), xe2x80x9cStability of Protein Pharmaceuticals,xe2x80x9d Pharm. Res. 6:903-918; Lai, M. C. and Topp, E. M. (1999), xe2x80x9cSolid-State Chemical Stability of Proteins and Peptides,xe2x80x9d J. Pharm. Sci. 88:489-500). Many of these degradation processes use water for hydrolysis and/or other degradation pathways. Therefore, many protein pharmaceuticals are prepared in the solid state as dry powders to prolong the useable shelf life of the product and the storage stability of the product. Protein unfolding in the dried solid can lead to irreversible denaturation upon immediate rehydration and significant reduction of long term storage stability.
Supercritical fluids are substances at a temperature and pressure above a critical temperature and pressure where the substance has a density, compressibility and viscosity intermediate between a gas and a liquid. Near-critical fluids are similar to supercritical fluids and are defined as fluids within 10% of the critical temperature and the critical pressure. For example, since the critical temperature of CO2 is 31.6xc2x0 C. (304.6K) and the critical pressure is 1073 psi, CO2 above 2xc2x0 C. (275K) and 966 psi is near-critical. Supercritical fluids have been researched for their use in the production of fine powders of pharmaceuticals, however these technologies (supercritical fluid nucleation (Larson, K. A. and King, M. L. (1986), xe2x80x9cEvaluation of Supercritical Fluid Extraction in the Pharmaceutical Industry,xe2x80x9d Biotechnol. Prog. 2:73-82), rapid expansion of a supercritical solution (Tom, J. W. and Debenedetti, P. G. (1991), xe2x80x9cPrecipitation of Bioerodible Microspheres and Microparticles by Rapid Expansion of Supercritical Solutions,xe2x80x9d Biotechnol. Prog. 7:403-41 1) and gas antisolvent techniques (Randolph, T. W. et al. (1993), xe2x80x9cSub-micrometer-sized biodegradable particles of poly(L-lactic acid) via the gas antisolvent spray precipitation process,xe2x80x9d Biotechnol. Prog. 9:429; Meyer, J. D. et al. (1998), xe2x80x9cPreparation and in vitro characterization of gentamycin-impregnated biodegradable beads suitable for treatment of osteomyelitis,xe2x80x9d J. Pharm. Sci. 87:1149; Winters, M. A. et al. (1996), xe2x80x9cPrecipitation of proteins in supercritical carbon dioxide,xe2x80x9d J. Pharm. Sci. 85:586; Palakodaty, S. et al. (1998), xe2x80x9cSupercritical fluid processing of materials from aqueous solutions: the application of SEDS to lactose as a model substance,xe2x80x9d Pharm. Res. 15:1835) require that the pharmaceutical be soluble directly in the supercritical fluid or be precipitated by the supercritical fluid from nonaqueous solvents such as dimethylsulfoxide. The nebulizer system disclosed in U.S. Pat. No. 5,639,441 (Sievers, R. E. and Karst, U., issued Jun. 17, 1997) and divisional application 08/847,310 permits the use of mixtures of supercritical fluids with immiscible liquids such as water to process substances that are not soluble in the supercritical fluid to form aerosols of vapors. Therefore, using the methods and devices disclosed in U.S. Pat. No. 5,639,441 particles of water soluble proteins, excipients, stabilizers, bulking agents and/or surfactants may be formed rather than just particles of those compounds that are soluble in supercritical fluids and/or organic solvents. U.S. Pat. No. 5,639,441 is hereby incorporated by reference, to the extent not inconsistent with the disclosure herein. Unlike the other precipitation methods, e.g., the SEDS process and GAS processes referred to above, no organic solvents are required in the new process; only the drug, water and the supercritical or near-critical fluid (for example, carbon dioxide) are needed.
Even though particles of water soluble proteins and other aqueous formulations can be prepared, no method to form suitable dry powders of these proteins and/or formulations existed until now. Existing technologies to produce dry protein powders, such as spray-drying, freeze-drying, or ultrasonic nebulization, suffer from a variety of problems. In general, dry protein powders are often irrevocably inactivated when produced by prior art methods because the processing steps involved in these methods, temperature required to dry the proteins using these methods and dehydration processes of these methods damage the delicate structure of the protein. Also, for use in direct inhalation applications, powders must be small enough to allow for effective pulmonary delivery. Drug delivery via a pulmonary route is preferred over other delivery routes such as injections for reasons such as decreased pain and delivery of the drug to the desired location more quickly. If the particles produced by the drying process are larger than desired, they must be jet-milled or mechanically ground. This creates an additional physical stress on the molecules and may impart a further loss of protein activity. Dry powders produced in the correct size region could be used directly in dry powder inhalers for pulmonary delivery.
Spray-drying is a currently-available method to produce dry protein powders. In the spray-drying technique, a jet nebulizer is used to form a plume of droplets. In one type of nebulizer, a liquid sample is sucked through a small diameter tube by a high-pressure stream of gas. The gas breaks up the liquid into fine droplets. The gas can also flow across the small diameter tube at right angles and form droplets in a similar manner. Ultrasonic nebulizers use ultrasonic vibrations coupled to the sample solution that cause the solution to break up into small droplets. One disadvantage of the method of spray-drying is the plume of molecules exiting the jet nebulizer is not very dense. This results in a process that is slow in producing a desired amount of protein. Freeze-drying is another currently used method to produce dry protein powders wherein aqueous solutions of drugs are frozen and placed under a vacuum to sublime the water. One disadvantage of the method of freeze-drying is the drying process is very slow. Also, the particles produced are relatively large, requiring additional processing steps to produce pharmaceutically desirable sizes.
U.S. Pat. No. 6,063,138 (Hanna, et al., issued May 16, 2000) and related EP 0767702 describes methods of forming particles of a substance by co-introducing a supercritical fluid; a solution or suspension of the substance in a first vehicle; and a second vehicle which is substantially miscible with the first vehicle and substantially soluble in the supercritical fluid into a particle formation vessel which is maintained at supercritical pressure and temperature.
PCT published application PCT/US99/19306 (WO 010541) (Edwards et al.) describes methods of forming particles by combining a bioactive agent, a phospholipid and an organic solvent or organic-aqueous co-solvent to form a mixture which is then spray-dried.
U.S. Pat. No. 5,695,741 (Schutt et al., issued Dec. 9, 1997) and related U.S. Pat. No. 5,639,443 (Schutt et al., issued Jun. 17, 1997) and U.S. Pat. No. 5,720,938 (Schutt et al., issued Feb. 24, 1998) describe xe2x80x9cmicrobubblesxe2x80x9d useful for magnetic resonance imaging and ultrasound imaging. The xe2x80x9cmicrobubblesxe2x80x9d are prepared by spray-drying a liquid formulation to produce microspheres having voids and then permeating the microspheres with a fluorocarbon gas osmotic agent.
U.S. Pat. No. 5,928,469 (Franks et al., issued Jul. 27, 1999) describes mixing materials with a carrier substance that is water-soluble or water-swellable and spray drying the resultant mixture to form particles containing both the material and the carrier substance in which the carrier substance is in an amorphous (glassy or rubbery) state. Franks describes spray drying at gas temperatures of 100 to 300xc2x0 C.
U.S. Pat. No. 6,001,336 (Gordon et al., issued Dec. 14, 1999) describes spray drying suspensions of a hydrophobic component and a hydrophilic component dissolved in an aqueous solution.
U.S. Pat. No. 5,851,453 (Hanna et al., issued Dec. 22, 1998) and related EP 0 706 421 describe a method and an apparatus for forming particulate products by introducing a supercritical fluid and a solution or suspension of a substance in a vehicle soluble in the supercritical fluid into a vessel which is maintained at controlled temperature and pressure. WO 95/01324 (York et al., published Jan. 12, 1995) describes particles of salmeterol xinafoate using this method.
WO 99/16419 (Tarara et al., published Apr. 8, 1999) describes preparing xe2x80x9cperforated microstructuresxe2x80x9d by atomizing a liquid and spray drying the liquid droplets that are formed. WO 00/00215 (Bot et al., published Jan. 6, 2000) describes delivery systems of xe2x80x9cperforated microstructuresxe2x80x9d containing xe2x80x9cbioactive agentsxe2x80x9d.
WO 99/59710 (Hanna et al., published Nov. 25, 1999) describes a method and apparatus for forming particles of a substance by dissolving or suspending the substance in a first vehicle which is or contains a first supercritical or near critical fluid and passing that solution or suspension into a particle formation vessel which contains a second supercritical fluid. The vessel is maintained at temperatures and pressures so that the second fluid remains supercritical.
WO 98/36825 (Hanna et al., published Aug. 27, 1998) describes a method and apparatus for forming particles by directing two supercritical fluids, one containing the substance of interest, into a heated and pressurized chamber.
There is a need for stable or pharmaceutically-active proteins in dry form, and a method to produce stable or pharmaceutically-active proteins in dry form. Also, there is a need to produce smaller particles with improved pharmaceutical activities.
This invention provides a method for forming fine dry particles comprising:
(a) forming a composition comprising one or more substances and a supercritical or near critical fluid;
(b) rapidly reducing the pressure on said composition, whereby droplets are formed;
(c) passing said droplets through a flow of gas heated from about 2xc2x0 C. to about 300xc2x0 C.
Preferably bubble drying should be conducted at temperatures above ambient temperature and below 100xc2x0 C. to minimize degradation of the pharmaceuticals. Given sufficient residence time and dilution, a flow of dry gas will dry the fine droplets without external heating. Heating accelerates drying by increasing the vapor pressure of water. The composition may also comprise an aqueous solvent.
Also provided is a method of forming fine dry particles comprising:
(a) mixing an aqueous solution containing the substance of interest and a supercritical or near supercritical fluid, forming a composition;
(b) rapidly reducing the pressure on said composition, whereby droplets are formed;
(c) passing said droplets through a flow of gas heated from about 2xc2x0 C. to about 300xc2x0 C.
Also provided is a method of forming fine dry particles comprising:
(a) equilibrating an aqueous solution of the substance of interest with a supercritical or near supercritical fluid, forming a composition;
(b) rapidly reducing the pressure on said composition, whereby droplets are formed;
(c) passing said droplets through a flow of gas heated from about 2xc2x0 C. to about 300xc2x0 C.
Also provided is a device for forming fine dry particles, consisting essentially of:
(a) a first pressurized chamber containing a first nongaseous supercritical or near critical fluid;
(b) a second chamber containing a solution or suspension of a substance in a second nongaseous fluid;
(c) a mixing chamber for mixing said solution or suspension and first fluid connected to said first and second chambers by conduits;
(d) first flow control means connected to the conduit between the first chamber and the mixing chamber for passing said first fluid into said mixing chamber;
(e) second flow control means connected to the conduit between the second chamber and the mixing chamber for passing said second fluid into said mixing chamber;
(f) a restrictor connected to said mixing chamber for conducting the composition out of the mixing chamber into a rapid expansion region having a pressure below that of the supercritical or near critical fluid where a dispersion of fine particles of said substance is formed;
(g) a drying chamber connected to the restrictor;
(h) a source of gas connected to the drying chamber at one or more inlets;
(i) means for collecting particles after they pass through the drying chamber.
The mixing chamber is preferably a low dead volume tee.
Fine particles are those with diameter less than about 5 micrometers. Particles formed by the methods of the invention may vary in diameter between about 0.1 micron to about 5 microns. The particles produced may be smaller than 0.1 microns, but current detection methods are size limited in the lower size range, and small particles do not constitute a significant fraction of the mass. The particles may be of any distribution of diameters. For certain applications, for example inhalation therapy, it is preferred that most particles be within the respirable range for delivery to the deep lung alveoli. Preferably the particles range in size from 1 to 3 microns for inhalation applications. Particles may be different sizes for other applications, as known to the art or readily determined without undue experimentation. It is preferred that for inhalation applications, the particles have a small variance from the average size.
As used herein, xe2x80x9cdryxe2x80x9d or xe2x80x9cdriedxe2x80x9d include particles that include some moisture, preferably not more than 5% by weight Dry particles include those particles which include from 0.0001% to 1% moisture, from 1% to 3% moisture, from 1% to 5% moisture, from 5% to 10% moisture, and combinations of those ranges.
Particles of various shapes are included within the invention. For example, particles may be hollow, or xe2x80x9cbubblesxe2x80x9d. Bubbles are hollow-centered, similar to a tennis ball or a ping pong ball, although they may not be as spherical as a tennis ball or a ping pong ball. The diameter of the particle is typically about 10 to 10,000 times the thickness of the skin. Other particles formed by the method of the invention are not hollow. Higher drying temperatures (xcx9c100xc2x0 C.) favors forming hollow particles, while the same substance may give solid spheres if dried slower at lower temperatures.
xe2x80x9cCompositionxe2x80x9d does not mean all substances are necessarily soluble in each other. Substances which may be made into particles by the methods of the invention include any substance which is either soluble in a supercritical fluid or near critical fluid or mixtures thereof; or a substance which is soluble or suspendable in an aqueous solution. The aqueous solution may also include various co-solvents, but avoiding the use of organic solvents may have environmental and toxicological benefits. Some substances which may be made into particles include: a physiologically active composition comprising one or more substances selected from the group consisting of surfactants, insulin, amino acids, enzymes, analgesics, anti-cancer agents, antimicrobial agents, viruses, antiviral agents, antifungal pharmaceuticals, antibiotics, nucleotides, DNAs, antisense cDNAs, RNAs, peptides, proteins, immune suppressants, thrombolytics, anticoagulants, central nervous system stimulants, decongestants, diuretic vasodilators, antipsychotics, neurotransmitters, sedatives, hormones, anesthetics, anti-inflammatories, antioxidants, antihistamines, vitamins, minerals and other physiologically active materials known to the art. Particles of monoclonal antibodies and vaccines may be produced. Particles of substances such as sodium chloride may also be produced. Some substances may be pharmaceutically-active. xe2x80x9cPharmaceutically-active proteinxe2x80x9d indicates that the protein has sufficient activity so as to be pharmaceutically useful. Other substances may not be physiologically or pharmaceutically-active.
Various additives may be used in the methods and particles of the invention. These additives may be added to the substance of interest or any solvent used in the process. Additives may also be added directly to the particles after formation. Additives include stabilizers, excipients, bulking agents and surfactants. The use of stabilizers in protein formulations protects against loss of protein activity upon drying. Stabilizers include, without limitation, sugars and hydrophilic polymers, such as polyethylene glycol, hydroxy ethyl starch, dextran or others. The stabilizer is preferably a sugar or mixture of different sugars. Sugars that can be used include mannitol, sucrose, lactose and trehalose, and other mono-, di-, and oligosaccharides. Addition of one or more stabilizers to the protein solution prior to dehydration significantly inhibits the conformational changes within the protein that are believed to be linked to a loss of enzymatic activity. One or more surfactants can be added to alleviate stresses between droplet/air interfaces and decrease degradation that may occur upon drying. Surfactants may be added to alleviate agglomeration or clumping that may occur upon drying. Surfactants are also thought to assist in the formation of spherical particles. Examples of surfactants that may be used include: polyoxyethylene (20) sorbitan surfactants (Tweens), such as Tween 20, Tween 40, Tween 80 and Tween 85; stearic acid; myrj (PEG monostearates), Span 85 (sorbitan trioleate) and polyether-carbonate block copolymers of the type reported in Beckman et al. (2000) Nature 405:165. Phospholipids, including phosophoglyceride may be used. Surfactants and other agents, such as guanidinehydrochloride, may facilitate protein refolding, coupled with pressure treatment. (St. John, R. J. et al. (1999) Proc. Natl. Acad. Sci. 96:13029). Bulking agents and excipients may be inert or active.
If needed for stability of the final formulation, buffer is preferably added first. If more stability is required, sugar may be added. If still more stability may be added, surfactant may be added. A pH buffering substance is useful to counteract the rapid drop in pH from carbon dioxide dissolution at high pressure to form carbonic acid.
For low potency drugs, the fraction of additives in the powder should be minimized; for high potency drugs, inactive excipients (diluents) sometimes constitute more than 99% of the mass. Additives may be added in any useful amount to the composition. Additives are typically used at a concentration of between about 0.001 to 0.5 wt % of surfactant (preferably between about 0.001 to 0.1 wt %), and between about 0.05 to 25% of stabilizer (preferably, when sugar is used, between about 0.1 to 20%, limited by the solubility limit of sugar) by weight to a solution comprising a protein of interest. These percentages are expressed for the aqueous solution before spraying and drying. The final percentage of sugar in the dried powder can be as high as xcx9c99.9%.
The composition may comprise a substance which is soluble in the supercritical or near critical fluid, such as a lipophilic compound. A mixture of supercritical or near critical fluids may be used. The composition may also comprise an aqueous solution or suspension of the substance and a supercritical or near critical fluid (or fluids). Droplets of substances which are not soluble in the supercritical or near critical fluid, such as hydrophilic substances, are then formed. In one embodiment of this method, an aqueous solution comprising a dissolved or suspended compound is pumped into a low-dead volume tee while a supercritical or near critical fluid is pumped into another leg of the tee. The resulting emulsion or supercritical solution pressurized to a pressure near or above the critical pressure of the supercritical fluid (about 70 to about 100 atmospheres when carbon dioxide is used) is allowed to expand to atmospheric pressure out a flow restrictor, forming fine droplets or bubbles containing the dissolved drug species. This aerosol is directed into a drying chamber where solvent evaporation and particle formation takes place.
A second variant of this method allows aerosols to be formed without a low-dead volume tee. In this method, an aqueous solution of precursors is first allowed to equilibrate with a near critical or supercritical fluid in a static canister or chamber, preferably with stirring or agitation. This composition is then allowed to expand to atmospheric pressure out of a flow restrictor, forming fine droplets. These droplets are directed into a drying chamber where solvent evaporation and particle formation takes place.
The initial concentration of the substance of interest in either the supercritical fluid or the aqueous solvent (or solvent mixture) is limited only by the solubility or saturation point of the substance in the solvent or supercritical fluid. Typical starting concentrations are about 1% to about 25% w/w of total solids in the solution or fluid.
Preferably the supercritical fluid is carbon dioxide because carbon dioxide is endogenous and relatively non-toxic, as well as having a critical pressure and temperature easily obtainable. Other supercritical or near-critical fluids may be used, provided that the critical temperature and pressure are obtainable and useful. Carbon dioxide is currently less expensive than any organic solvent and its use avoids VOC emissions. Carbon dioxide""s solubility in water is about 2% at 100 atm at near-ambient temperatures.
A number of fluids suitable for use as supercritical fluids are known to the art, including carbon dioxide, sulphur hexafluoride, chlorofluorocarbons, fluorocarbons, nitrous oxide, xenon, propane, n-pentane, ethanol, nitrogen, water, other fluids known to the art, and mixtures thereof. The supercritical fluid is preferably carbon dioxide or mixtures or carbon dioxide with another gas such as fluoroform or ethanol. Carbon dioxide has a critical temperature of 31.3 degrees C. and a critical pressure of 72.9 atmospheres (1072 psi), low chemical reactivity, physiological safety, and relatively low cost. Another preferred supercritical fluid is nitrogen.
The gas that contacts the flow of the droplets is preferably inert, and a preferred embodiment is nitrogen gas, but the gas may be chosen so as to react with the molecule of interest in the course of drying. Preferably the flow of gas contacting the flow of the sample forms a sheath surrounding the flow of the sample, but the flow of gas may contact the flow of the sample by other means such as turbulent mixing. Preferably this gas is heated to a temperature sufficient to cause the desired level of particle drying and also not substantially degrade the biological activity of particles. The gas may be heated to between about 2xc2x0 C. to about 300xc2x0 C., preferably below 100xc2x0 C., although depending on the substance being dried and the constituents of the composition, the temperatures may be adjusted. A preferred range of drying temperatures is between about 35xc2x0 C. to about 100xc2x0 C.
Preferably the gas is contained in a drying chamber such as a drying tube. The drying tube is as long as necessary to produce particles having the desired level of moisture by the time the particles reach the end. The drying tube is preferably larger than the diameter of the droplet plume formed from the rapid expansion. The drying tube may be heated, but that is not required. Preferably most of the heat required for vaporizing water is provided by heating the drying gas before it enters the drying chamber. Heating the drying tube may assist in preventing condensation on the surfaces of the tube. The drying tube may be heated externally by means of a lamp such as an infrared lamp, or internally by any means known in the art such as a heating wire imbedded in the material making up the tube. The drying tube may be made from any suitable material which can withstand the temperatures to which it is subjected. Examples of material from which the drying tube can be made are stainless steel or borosilicate glass. Any other design of drying chamber may be used if the desired results are obtained. Other apparatuses, for example a microwave oven, may be used in place of the drying tube to perform the same function.
Rapid reduction of the pressure of the composition is typically performed using a flow/pressure restrictor. The restrictor may be a hollow needle of an thermally conductive material such as stainless steel or a ceramic material, or other material which is able to withstand the pressure and temperature placed upon it. The restrictor may alternatively be a fused silica flow restrictor, or a ceramic multi-channel bundle of capillaries such as that discussed in more detail elsewhere. Also, high pressure sintered stainless steel filters may be used to generate aerosols. The length of the restrictor is typically about 2 inches long; however, the length must not be so long as to cause low flow rates or the precipitation of sufficient solid substance in the restrictor to cause clogging. The restrictor may have as large a diameter as desired, as long as the desired size particles are formed and the pumps have sufficient capacity to maintain the pressure. The lower limit of diameter is determined by the viscosity of the solution being passed through the restrictor. If the viscosity is too high, particles are not formed.
The invention also provides a multichannel restrictor. These openings may be spaced approximately the same distance from each other. The structure may have a cylindrical, a hexagonal, or other shape which allows it to be coupled with the other components used. The openings may be any suitable shape, such as round or hexagonal. An embodiment of one such structure has about 900 non-concentric parallel channels in about a 2 mm total diameter. This multichannel restrictor may have a total diameter which provides the desired particle formation. Preferably each channel has an inner diameter between about 40 xcexcm and about 125 xcexcm. Other multichannel structures may be used, and the openings do not need to be a similar size, although it is preferred if the openings are similarly sized.
The exit tip of the restrictor structure may be flat or substantially flat, or may be shaped. One shape that is particularly useful is formed by removing material from the sides of a flat end, to form an elongated point, similar to a pencil. This modification gives a more dispersed stream of droplets emitted over a 180xc2x0 angle which is useful to assist in preventing agglomeration of particles as they undergo bubble drying. The particular geometry which gives the best results, depending on the results desired, may be discovered by routine experimentation. Any other means available for reducing the pressure on a composition may be used to accelerate drying.
With many openings through which the composition may pass, the flow rate through the system may be increased and the throughput of the system increased. The overall throughput rate is principally controlled by the total inner diameter of the flow restrictor. Various inner diameters of single channel restrictors may also be used, including 75 micron, 100 micron, 170 micron, and 200 to 1000 micron. Another benefit of multi-channel restrictors over single channel ones is that if one channel becomes clogged, the remainder of the channels remain functional.
The method of this invention may be used for processes in which faster drying than currently available is desired. Fast drying may occur because the swelling/bursting processes of the invention gives greater surface area for drying, although applicants do not wish to be bound by this theory.
Various particles including pharmaceutically-active protein compositions in dry form comprising particles of a protein of interest and optionally containing one or more additives selected from the group consisting of excipients, stabilizers, bulking agents and surfactants, wherein the additives are present at a concentration of about 0.001% to about 99.9%, measured by weight of the dry protein, and wherein the particles have diameters of about 0.1 microns to about 10 microns are produced by the method of this invention. Particles may have a variety of bulk densities depending on the particular substances involved and the conditions under which particle formation and drying occur. For example, particles with bulk densities of between about 0.1 and 1.5 g/cm3 may be formed. The bulk density may be less than 1 g/cm3, less than 0.8 g/cm3, less than 0.5 g/cm3, less than 0.4 g/cm3 or other ranges. Particles may have a variety of activities after rehydration. For example, dry particles with at least 90% of the original activity upon rehydration are included in the invention. Particles with 90-95%, 90-100%, 100-120% original activity are also among those included in the invention.
The particles may be stored in any convenient manner after formation and drying, including placing in bags or other storage devices or additional drying during storage over desiccants such as P4O10 can be undertaken.
The invention also provides a nebulization system using an injection port that requires a lower volume of sample than currently available systems. This is an advantage when conducting laboratory scale experiments, for example, on costly samples. The injection port also permits equilibration of the nebulization and drying system with the solvents only, followed by introduction of a solution comprising the protein of interest after the system has been equilibrated. This reduces waste of the protein. This nebulization system may be attached to a bubble drying system, or may be coupled with equipment used in conventional spray drying to permit faster drying at lower temperatures.
A method of making droplets by injecting a volume of one or more substances into a flow of a solution comprising an aqueous or supercritical or near supercritical solution using a means for introducing a small sample volume into the flow and subjecting the resulting solution to a rapid pressure decrease to form droplets is provided. Preferably the introducing means is an injection port, such as that used for HPLC. Preferably the volume introduced is about 0.1 mL to about 10 mL.
A method of delivery of proteins or other substances comprising: drying a protein or other substance using the method of this invention, reconstituting the protein with water or other suitable substance, and delivering via desired means is provided.
Stable and/or pharmaceutically active particles are also provided. xe2x80x9cStablexe2x80x9d means resistant to decomposition during storage, shipping, reconstitution, and administration.
A device for rapid expansion of a composition comprising a low dead volume tee through which said composition passes and a restrictor with more than one substantially parallel non-concentric channels affixed to said tee is also provided. A low dead volume tee is a mixing tee having a volume of about 0.2 to 10 xcexcl. The tee may be affixed to the restrictor by any suitable means, for example, epoxy or appropriate fittings.
The drying technique of the invention has advantages over conventional drying techniques. The drying technique of the invention is scalable without significant alteration of particle size or morphology. The method also provides particles having lower density than particles produced by other methods. This leads to particles with small aerodynamic sizes, but large absolute particle dimensions, since in one embodiment, additional gaseous supercritical fluid is formed and leaves the substance of interest containing particles with porous or hollow structures. This permits larger particles with lower momentum to reach the deep lung than would otherwise be possible, in one application.